Electronic system for monitoring drilling conditions relating to oil and gas wells



3,541,852 TIoNs NOV. 24, 1970 J, H, BROWN ETAL ELECTRONIC lSYSTEM FORMONITORING DRILLING CONDI 'RELATING To OIL AND GAS WELLS Filed Nov. 29,1968 5 Sheets-Sheet l wmv IIIIIIIIIIIIIIMIIIII'L Nov. 24, 1970 H BROWNET AL 3,541,852 ELECTRONIC SYSTEM FOR MONITORING DRILLING CONDITIONSRELATING TO OIL AND GAS WELLS Filed Nov. 29, 1968 5 Sheets-Sheet zAMPLIFIER ONE SHOT 45' 47 37 gLLgR GATE RECORDER 48 W 49 r55 INTERLOCKCcg'flTER DRIVER an- J V COUNTER 50 Iozl 5I COUNTER IO: I

/52 FIG 2 |ACCUII/IULATOR l 53 DIODE MATRIX BUFFER 54 l READOUT lINvENToRs WILLIAM M. i DEASON JAMES H. BROWN WI LLIAM S. YOUNG ATTORNEYNOV. 24, 1970 1 H, BROWN ET AL 3,541,852

ELECTRONIC SYSTEM FOR MONITORING DRILLING CONDITIONS RELATING TO OIL ANDGAS WELLS Filed NOV. 29, 1968 5 Sheets-Sheet 3 +D.c. VOLTAGE JAMES H.BROWN WILLIAM S. YOUNG LLDJJIQQL F- AT ORNEY J. H. BROWN ET AL Nov. 24,1970 ELECTRONIC SYSTEM FOR MONITORING DRILLING CONDITIONS RELATING TOOIL AND GAS WELLS 5 Sheets-Sheet 4 Filed NOV. 29, 1968 dvd+? INVENTORSWILLIAM M. DEASON JAMES H. BROWN WILLIAM S. YOUNG ATTOR EY I pm.

NOV. 24, 1.970 J, H, BROWN ETAL 3,541,852

ELECTRONIC SYSTEM FOR MONITORING DRILLING CONDITIONS RELATING To OIL ANDGAS WELLS 5 Sheets-Sheet 5 Filed Nov. 29, 1968 FIG. 6

INVENTORS WILLIAM M. DEASON JAMES H- BROWN WILLIAM SfYOUNG 0.2m OWNATTORNEY United States Patent O 3,541,852 ELECTRONIC SYSTEM FORMONITORING DRILLING CONDITIONS RELATING TO OIL AND GAS WELLS .lames H.Brown, William S. Young, and William M. Deason, Houston, Tex., assignorsto Dresser Industries, Inc., Dallas, Tex., a corporation of DelawareFiled Nov. 2.9, 1968, Ser. No. 780,041 Int. Cl. E21b 45 00 U.S. Cl.73-151 19 Claims ABSTRACT OF THE DISCLOSURE An electronic systemself-contained within a skid or trailer-mounted console provides acompletely new set of well statistics once each minute or once eachfoot, thus giving the drilling operator a continuous picture of drillingconditions. Information recorded by the system includes drilling depth,time, penetration rate, hook load, rotary speed, pump strokes, gaschromatography, and such drilling mud information as weight-in,weight-out, viscosity and temperature and flow rates. A drilling mud pitvolume totalizer sub-system includes mean for monitoring the mud volumein each of a series of drilling mud pits, means for adding theindividual volumes to monitor the total mud volume in the system andalso means to include the residual drilling mud located beneath the mudlevel sensors Within the total mud volume. Also included within thesystem is mechanical apparatus and associated electronics for monitoringthe true depth and rate of penetration of the drill bit and associateddrill pipe and also the speed of rotataion of the drill bits.

BACKGROUND OF THE INVENTION This invention relates to a system forproviding a continuous indication of drilling conditions relating to thedrilling of oil and gas wells. In particular, the invention relates toan electronic system wherein the drilling operator is provided acomplete prole of up-to-date well statistics, thus giving the operator acontinuous picture of drilling conditions.

In the art of drilling oil and gas wells, the drilling operatorfrequently drills at less than peak penetration rates because of theever constant danger of blow-outs. Such blowouts are commonly caused bythe existence of a formation pressure a the bottom of the drilled holewhich exceeds the hydrostatic pressure of the drilling mud column withinthe hole, thus creating a condition whereby formation uids are caused toflow into the well bore. These formation fluids, which commonly may begas, oil, water, or combinations thereof, have low densities and thepressure difference which caused their ilow becomes even greater asthese extraneous fluids rise in the well bore, thus displacing drillingmud out of the top of the casing. Whenever this occurs, a blowout isimminent unless the pressure difference which caused the formation fluidto ilow into the well bore is controlled, as for example, by closing ablowout preventer such as is usually provided at the top of the well.Because of the fact that blowouts are extremely dangerous and quiteexpensive,

many devices have been built and are used in the drilling art in anattempt to control and eliminate blowouts. For example, a system forkilling oil and gas wells whenever a blowout is imminent is described inco-pending application U.S. Ser. No. 692,458, led Dec. 21, 1967,assigned to the assignee of the present invention. However, while such asystem as is described in said co-pending application has beensuccessful in the automatic control of an oil and gas well, thereremains the ever present need for a system with improved monitoring andrecording capability.

It is therefore the primary object of this invention to provide a systemhaving improved monitoring capability relating to the drilling of oiland gas wells;

It is another object of this invention which provides a new and improvedprofile of the conditions relating to the drilling of an oil and gaswell;

It is also an object of this invention to provide a system havingimproved capability for monitoring the total drill mud volume within thepits used in the drilling of an oil and gas well;

It is still another object of the invention to provide a new andimproved system for monitoring the rate of penetration of a drill bitused in drilling an oil and gas well; and

It is another object of the invention to provide a new and improvedsystem for monitoring the speed of revolution of a drill bit used indrilling an oil and gas well.

The objects of the invention are accomplished, generally, by a systemwherein the drilling parameters and mud information parameters arecontinuously monitored to provide a continuous profile of the drillingconditions. An electronics sub-system provides a continuous monitoringof total drill mud volume which is corrected for the residual mud volumewithin the drill mud pits. There is also provided a mechanical andelectronic sub-system for continuously monitoring the rate ofpenetration and also the total amount of penetration of the drill bitand associated drilling pipe, as well as the speed of rotation of thedrill bit.

Other objects, advantages, and features of the invention will be evidenthereinafter in the more detailed description of the invention.

In the drawing, which illustrates the preferred embodiments and modes ofoperation of the invention and in which like reference charactersdesignate the same or similar parts throughout the several views:

FIG. l is a schematic block diagram of the system according to theinvention;

FIG. 2 is a schematic diagram of the apparatus and associatedelectronics for monitoring the total depth and rate of penetration ofthe drill bit according to the invention;

FIG. 3 schematically illustrates the switch closure mechanism andassociated electronics for monitoring the speed of rotataion of thedrill bit;

FIG. 4 illustrates schematically a circuit according to the inventionfor monitoring the total mud volume within the pits;

FIG. 5 illustrates schematically in more detail one of the balancedampliers shown in block diagram in FIG. 1; and

FIG. 6 illustrates schematically the apparatus used for determining therate of rotation of the drill bit and also the apparatus used formeasuring the total depth and rate of penetration of the drill bit.

Referring now to the drawing in more detail, especially to FIG. l, thereis illustrated in block diagram a system according to the presentinvention, A drilling platform 10, through which an earth borehole hasbeen drilled, denoted generally by the reference numeral 11, has anR.O.P. (rate of penetration) and depth unit 12 mounted thereon. A pairof mud pumps 13 and 14 are used to pump conventional drilling mud intoand out of the well bore, all as is known in the art. The mud pumps 13and 14 first pump the mud into the standpipe line 18, where it is thenpumped into the earth borehole. In returning from the earth borehole,the mud returns through the fiow line 19 into the shaker pit 17, andthereafter into the mud pit 16 and the suction pit 15. The mud is thenreturned into the mud pumps 13 and 14, In the system according to thepreferred embodiment of the invention, there is provided in thestandpipe line 18 a conventional pressure sensor 20 which is used tomonitor the mud pump standpipe pressure. There is also provided a sensor21, for example, either a buoyant ball or a beam balance, which is usedto monitor the weight of the mud in the fiow line 19. Each of the mudpits 15, 16 and 17 has a sensor, respectively identified as sensor 22,23, and 24, which is used to monitor the amount or volume of mud withinthe pits, all as is described hereinafter in more detail with respect toFIG. 4. Such a sensor is preferably of the resistance type, for example,a Metritape sensor available from Metritape Controls, Inc. of WestConcord, Massachusetts, wherein a change in resistance is indicative ofa change in the mud level. Associated with the mud pumps 13 and 14 are apair of sensors 25 and 26, for example, a micro-switch responsive to thepump, which provide electrical indications of mud pump strokes perminute. A sensor 27, described in more detail with respect to FIGS. 3and 6 hereinafter, provides an indication of the rotary speed of thedrill bit associated with the system. A sensor 28 provides an indicationof the hook load within the system, for example, the conventional hookload indicator available from Bell Engineering in Odessa, Tex. Aconventional sensor 29 within the suction pit 15 provides an indicationof the mud weight within the suction pit.

As is better described with respect to FIG. 4, the electrical outputs ofthe sensors 22, 23 and 24 are combined within the circuitry identifiedgenerally as mud volume 30 in FIG. 1 to provide an indication of totalmud volume.

The electrical outputs from the sensors 20, 21, 22, 23, 24, 25, 26, 27,28 and from the depth unit 12 are cornbined at the junction box 31. Itshould be appreciated that all of the circuitry and apparatus thus fardescribed are generally associated with the drilling rig platform andmud pits.

The portion of the system shown within the dotted lines 32 in FIG. 1 ispreferably mounted within a skid or trailer-mounted unit which can betransported to the site of the drilling platform. Within the dottedlines 32 is found a distribution panel 33 into which the connections aremade from the junction box 31. It should be appreciated that there wouldnormally be a cable approximately two hundred feet in length joining thejunction box 31 and the distribution panel 33. Coupled to the output ofthe distribution panel 33 is a group of balanced amplifiers within thebox generally identified as balance amplifier panel 34. A typicalbalance amplifier as is found within the panel 34 is illustrated in moredetail with respect to FIG. 5 hereinafter. An R.O.P. and depthconversion unit 35, described in detail with respect to FIG. 2, iscoupled into the distribution panel 33 and also into ananalog-to-digital converter section 36 which preferably has a multiplexinput. Although not illustrated in detail,

the system according to the invention has a clock built into thecircuitry allowing time to be entered into the print-out, for example,on the recorders 37 and 38. Further, the multiplexing and monitoringoperations are timed for print-out once each minute. The gaschromatography section, not illustrated, makes use of a five point gaschromatograph on a two minute cycle, the output of which is recorded ona time drive chart, the time and depth markers on the chart being keyedto the time and depth on the automatic typewriter report from therccorder 38.

A conventional analog recorder 37, for example, a Strip chart recorder,is coupled into the output of the balance amplifier panel section 34. Adigital recorder 38, for example, a digital typewriter, is coupled tothe output of the analog-to-digital converter 36.

Referring now to FIG. 2, there is illustrated a wheel 40 which rotatesin response to the movement of the kelly and traveling block illustratedin FIG. 6. For purposes of FIG. 2, however, the Wheel 40 is caused torotate in response to the movement of the cable 41. The wheel 40 has acircumference of two feet. `Coupled to the wheel 40 is another wheel 42which creates a mechanical step-up of 20 rotations for the Wheel 42 forevery rotation of the wheel 40. Through the belt 43, the wheel 42 causesthe shaft 44 to rotate and thus drive the rotational encoder mechanism45. Although there are various means known in the art for convertingrotational movement into electrical pulses, the mechanism 45 can be, forexample, an encoder such as is described in the co-pending applicationU.S. Ser. No. 577,345, filed Sept. 6, 1966 now U.S. Pat. 3,426,303 andassigned to the assignee of the present invention. The output of themechanism 45 produces one hundred electrical pulses, each preferablyhaving a square wave output, for each revolution of the shaft 44. Theoutput of the apparatus 45 is coupled into a conventional filter andbuffer section 46 and then into a gate circuit 47. Also coupled into thegate 47 is an interlock circuit 48, which may be, if desired, merely amanual switch which may be operated by the operator to close the gate 47Whenever the cable 41 reverses direction. Such an interlock is desirableto thus provide an electrical indication of travel only whenever thetraveling block and kelly assembly, illustrated in FIG. 6, is moving inthe downward direction. If desired, however, the interlock circuitry 48can be automatically responsive to the movement of the kelly in adownward direction and also act to close the gate 47 whenever the kelly1s moving in the upward direction, as, for example, through a one-wayclutch. If desired, the interlock circuit 48 could be made automaticallyresponsive to a given speed of the drill bit, to Weight on the bit, ormud pump pressure, to name but a few examples. The output of the gate 47is seen to travel in two directions. In the one direction, the output ofthe gate 47 drives a series of electronic counters 49, 50 and 51, eachof said counters preferably having a 10:1 ratio. Thus, for each of thecounters having such a ratio, for each ten pulses into the counter, onlyone pulse is seen on its output. The output of the counter 51 is thencoupled into a conventional accumulator circuit 52 which drives a diodematrix and buffer circuit 53 which in turn drives the readout section54. It should be appreciated that the readout section 54 is not arecorder, but merely the point at which the circuit output appears.

In the operation of the circuit of FIG. 2 thus far described, it is seenthat since the wheel 40 has a circumference two feet and because thewheel 42 bears a 1:20 ratio to the wheel 40, the shaft 44 makes 20revolutions for each two feet of travel of the cable 41. For each onefoot of travel, the shaft 44 makes ten revolutions. Since the device 45creates one hundred pulses per revolution, the output of the device 45is thus seen to be one thousand pulses per one foot of travel of thecable 41. Since the series of counters 49, and 51 create a reduction ofone output for each one thousand pulses in from the gate 47, it shouldbe appreciated that the output of counter 51 therefore causes there tobe one pulse per each foot of travel of cable 41. The output of theaccumulator 52, as represented by five decades of BCD readout having 21lines, is then coupled into the diode matrix 53 to drive the readoutcircuit 54.

The output of counter 49, having an electrical output of one hundredpulses for each foot of travel of the cable 41, is coupled into thedriver circuit 55 which drives the recorder 37, for example, a pulsedriven recorder commercially available from Texas Instruments,Incorporated of Dallas, Texas, such a recorder thus being driven as afunction of movement of the cable 41, and hence depth of the drill bit.Such a recorder conventionally has a vertical scale wherein five inchesis representative of 100 feet of travel. Since the output of the counter49 is 100 pulses per foot of travel, the driver circuit 55 converts the100 cycle per foot information into that necessary to cause one inch oftravel by the recorder paper in the recorder 37 for every 20 feet oftravel by the cable 41.

The output of gate 47 is also connected into a one shot multivibrator60, the output of which is coupled into a filter 61 to drive anoperational amplifier 62. The output of the amplifier 62 is coupled intoan attenuator 63 to drive the recorder 37. Since the output of theamplifier 62 is indicative of the rate at which the one shotmultivibrator fires, the output of the amplifier 62 is indicative of therate at which the cable 41 is moving and hence the rate of penetrationof the drill bit used in conjunction with the system. The output of theamplifier 62 is preferably set from 0 to 5 volts D.C., the

amplitude of which is directly proportional to the rateof penetration ofthe drill bit. Since the recorder 37 is driven in conjunction with thetotal depth at which the drill bit is found, it should be appreciatedthat the rate of penetration of the drill bit is recorded as a functionof depth of the drill bit on the recorder 37.

Referring now to FIG. 3, there is illustrated circuitry which convertsthe rotation of the drill bit into a DJC. voltage which is linear withrespect to the rotary speed of the drill bit. Within the dotted linearea 27 there is illustrated a switch 71 which may be used to indicatethat the kelly and drill pipe stem as illustrated in FIG. 6 are rotatingat a determinable speed. In the preferred embodiment, the switch 71 iscaused to be closed once per each revolution, as is explained in moredetail with respect to IFIG. 6. As further illustrated in FIG. 3, theclosure of the switch 71 causes the positive D.C. voltage on the line72, for example, 15 volts, to be applied through the capacitor 73 intothe inverting input 74 of the amplifier section 75. It should beappreciated that the amplifier section 75 and its associated electroniccomponents 73, 76, 77, 78, 79, 80, 81, 82, 83, 84 and 85 comprise a oneshot oscillator and trigger section responsive to the closure of theswitch 71 which causes a single voltage pulse to be delivered throughthe diode and resistor 91 into the base of the transistor 92 for eachclosure of the switch 71. The transistor 92 and the circuit elements 93,94, 95, 96, 97 and 93 together comprise an interstage coupling invertersection. The output of the transistor stage 92 is coupled from thecollector element of the transistor 92 through the resistor 97 and theresistor 99 into the non-inverting input of the amplifier 101. Theamplifier section 101 along with the component parts 102, 103, 104, 105,106, 107, 108, 109 and 110 together comprise a signal output and filtersection, the output of which is a D.C. voltage which is linear withrespect to the number of contact closures per unit time of the switch71.

6 The following table (Table One) lists the values of the componentparts corresponding to those illustrated in FIG. 3:

It should be appreciated that the operational amplifiers identified as709cs are available from Fairchild Semiconductor in Mountain View,California. Since all the 709cs are identical, and have pins numbered1-8, inelusive, the pins are so numbered in the drawing.

FIG. 4 illustrates schematically in more detail the R.O.P. and depthconversion circuit 35 of FIG. l. Since there are three substantiallyidentical circuits connected to the output of the sensors 22, 23, and 24in FIG. 4, only one such circuit will be described in detail. The sensor22, being a resistance type device inserted within the mud in thesuction pit 35, is coupled into a balanced bridge circuit comprising theadditional resistors 120, 121, and 122. A trimming potentiometer 162 isconnected across resistor 122. The junction between resistors 121 and122 is connected through resistor 12.3 into the inverting input of theamplifier 124. The other end of the resistor is coupled into thenoninverting input of the amplifier 124. The amplifier 124 is connectedas a differential amplifier to detect the difference between thevoltages occurring at the two inputs. The output of the differentialamplifier 124 is coupled through the potentiometer 125 and resistor 126into the summing junction 127. In a similar manner, the other twocircuits, being indicative of the electrical signals from the sensors 23and 24, are coupled through potentiometers 128 and 129, respectively andthrough the resistors 130 and 131, respectively, to the summing junction127. Also connected into the summing junction 127 is a voltage from thepotentiometer 132 which is indicative of the residual mud within thepits, such an indication being necessitated by the fact that the sensorswithin the mud pits normally do not extend all the way to the bottom ofthe pit. Thus, by setting the potentiometer 132 and coupling the voltagefrom that potentiometer through the resistor 133 to the summing junction127, the voltage appearing at junction 127 is the sum of the signalsfrom the sensors 22, 23, 24 and from the potentiometer 132. Theamplifier 150 is connected as a summing amplifier to be responsive tothe voltage appearing at the terminal 127. The voltage thus appearing atthe output terminal 151 of the summing amplifier 150 is a linear D.C.voltage which is proportional to the total volume in the mud pits 15, 16and 17 of FIG. l. The potentiometer 152 is used to adjust the balance ofthe summing amplifier 150.

The value of the components enumerated in FIG. 4 are set forth in thefollowing table:

TABLE TWO Component: Value 2.7K ohm. 121 2 7K ohm. 122 330 ohm. 123 47Kohm. 124 709C. 125 100K ohm potentiometer. 126 100K ohm. 128 100K ohmpotentiometer. 129 100K ohm potentiometer. 130 100K ohm. 131 100K ohm.132 5 0() ohm potentiometer. 133 100K ohm. 134 100K ohm. 135 1.5K ohm.1.36 .()1 pf., 200 volt. 137 47 ohm. `138 .001 pf., 200 volt. 139 47ohm. 140 10() pf., 30 volt. 141 0.1 ttf., 200 volt. 142 .01 ttf., 200volt. 143 100 pf., 30 volt. 144 47 ohm. 145 .01 af., 200 volt. 146 100af., 30 volt. 147 470K ohm. 148 1.5K ohm. 149 .01 pf., 200 volt. 150709e. 152 `100K ohm potentiometer. `153 100K ohm potentiometer. 154 .0011,200 volt. 155 100 pf., 30 volt. 156 .01 pf., 200 volt. 157 47 ohm. 15815K ohm. 159 4.7K ohm. 160 IN751, 5.1 volt Zener. 161 1.8K ohm. 162 500ohm potentiometer.

FIG. 5 schematically illustrates one of the balanced amplifier sectionswithin the balance amplifier panel 34 of FIG. 1. As illustrated in FIG.5, either a D.C. or an A.C. input can be coupled through the terminalsand 171, respectively, the A.C. input then being coupled through acapacitor 172. The signal or signals are then coupled through resistor173 and may then be coupled into either the inverting input through theresistor 174 or directly into the non-inverting input. The switch 175 isused merely to indicate that one has a choice of input, inverting ornon-inverting, to the amplifier 176. It should be appreciated that thepotentiometer 177 and resistor 178 provide D.C. balance for the amplier.Likewise, the potentiometer 179 is used to control the gain of thebalance amplifier. Thus, the output appearing at the F terminal 180 is aD.C. voltage which tends to facilitate the use of the information fromthe various sensors throughout the system for the conversion from analogvoltages to digital voltages as accomplished Within theanalog-to-digital converter 36 of FIG. 1. The circuit in FIG. S servesseveral functions within the system accordto the invention. It first ofall provides a constant input impedance into the analog-to-digitalconverter 36. The circuit also provides a means for adjusting the gainor amplitude of the signals from the individual sensors. The circuitalso provides a means for nulling out any noise within its associatedsignal channel. However, perhaps the most important feature of thecircuit resides in its ability to match the calibration slope of a givensensor. The sensors themselves each have linear responses. The outputoutput of the illustrated balance amplifier is a linear D.C. voltage. Bythe use of the gain control 179 and the balance control 177, the slopeof the output curve appearing at junction 180 can be made to closelymatch the calibration slope of the given sensor.

It should be appreciated with this particular type of' operationalamplifier 176, as Well as with the amplifiers used in the circuits ofFIGS. 3 and 4, that the preferred positive D.C. voltage is l5 volts.

The values for the components of FIG. 5 are enumerated in the followingtable:

TABLE THREE Component: Value 172 5 af., l5 volt. 173 47K ohm. 174 5.1Kohm. 176 709e. 177 100K ohm potentiometer. 178 10M ohm. 179 100K ohmpotentiometer. 181 47 ohm. 182 .0l af., 200 volt. 183 100 pf., 30 volt.184 .U01/tf. 185 1.5K ohm. 186 .0l af. 187 150K ohm. 188 10K ohm. 18910K ohm. 190 30K ohm. 191 47 ohm. 192 100 af., 30 volt. 193 .0l pf., 200volt.

FIG. 6 illustrates schematically a pair of the sensors connected to thedrilling rig apparatus. In FIG. 6, there is shown a borehole 200 (thelower portion of borehole 11 in FIG. l) penetrating the earth and inwhich is arranged a drill string 201, to the lower end of which isattached a drill bit (not illustrated). At the earths surface isarranged surface drilling equipment including a derrick 202. The hose203 is connected to a mud standpipe (not illustrated), the hose 203being connected to the swivel assembly 204. The kelly 205 is connectedthrough the well head 206 to the drill pipe 201 in the conventionalmanner. Attached to the kelly 20S is a block of metal 207 capable ofaffecting an adjacent magnetic field which is caused to rotate as thekelly member rotates. Attached to the swivel member 204 is anon-rotating detector 27 having a built-in permanent magnetic fieldhaving contacts 71 which may be, for example, a read relay, which iscaused to be actuated by the passing of the metal block 207 as the kellyrotates. It should be appreciated that the switch closure means 71within the detector 27 corresponds to the switch 71 in FIG. 3. It shouldbe appreciated further, that as the kelly 205 rotates, the drill pipe201 also rotates with the drill bit, and hence the closure of the switch71 is indicative of the rate of revolution of the drill bit.

Also illustrated in FIG. 6 is an apparatus for measuring the total depthand rate of penetration of the drill bit. Attached to the swivel member204 is a cable 41 which passes over a wheel 210 attached to the frame ofthe derrick 202. The cable 41 also passes over the wheel 40 to cause thewheel 40 to turn directly proportional to the amount of travel of thecable 41. After passing over the Wheel 40, the cable 41 is wound upon adrum 211, the drum 211 being preferably provided with a suitablemechanism such as a spring motor (not illustrated) which is normallybiased to rotate the. drum in a direction to wind the cable 41 thereonbut yet is yieldably responsive to the pull of the cable 41 to permitunwinding of the cable from the drum 211. The cable 41 is thus fullycapable of closely following the movement of the drill string. It shouldbe appreciated that the wheel 40 as the cable 41 is caused to move bythe kelly being moved downward, that the electronic circuitry describedherein provides a measure of the depth and rate of penetration of thedrill bit.

It should thus be appreciated that there has been described herein a newand improved system for continuously monitoring important parametersrelating to the drilling of oil and gas Wells, such a system providing acontinuous readout to the drilling operator. Although the preferredembodiments of the invention have been illustrated and described indetail, modifications of the embodiments illustrated herein will occurto those skilled in the art and it is contemplated that suchmodifications and changes as are within the spirit of the invention areto be Covered by the scope of the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. In an earth borehole drilling system having a drill rig and a drillmud pit associated therewith, a mud volume sub-system comprising:

a mud-sensitive sensor mounted in said mud pit;

first electrical circuit means responsive to said sensor producing a rstelectrical signal functionally related to the mud level in said pit;

second electrical circuit means for producing a second electrical signalindicative of a residual amount of mud in said pit undetected by saidsensor; and

means to combine said lirst and second electrical signals to provide anindication of the mud volume in said pit.

2. In an earth borehole drilling system having a drill rig and a drillmud pit associated therewith, a mud volume sub-system comprising:

a mud-sensitive sensor mounted at a given level in said mud pit;

first electrical circuit means responsive to said sensor producing aiirst electrical signal functionally related to the mud level in saidpit;

second electrical circuit means for producing a second electrical signalindicative of a volume of mud in said pit beneath said given level; and

means to combine said first and second electrical signals to provide anindication of the mud volume in said pit.

3. In an earth borehole drilling system having a drill rig and aplurality of drill mud pits associated therewith, a mud volumesub-system comprising:

a plurality of mud-sensitive sensors, one of said plurality of sensorsbeing mounted in each of said mud pits;

a plurality of electrical circuit means respectively responsive to saidplurality of sensors, whereby a plurality of electrical signals areproduced functionally related, respectively, to the mud level in each ofsaid pits;

an additional electrical circuit means for producing an additionalelectrical signal indicative of a combined residual volume of niud insaid pits undetected by said sensors; and

means to combine said plurality of electrical signals with saidadditional electrical signal to provide an indication of the combinedmud volume in said plurality of pits.

4. In an earth borehole drilling system having a drilling rig whereindrill pipe and associated drill bit penetrate the l f earths surface, atotal depth of penetration sub-system comprising:

means to translate the linear motion of the drill pipe into rotarymotion; means to translate said rotary motion into a series ofelectrical pulses; means to count said electrical pulses, whereby saidcount provides an indication of the depth of penetration; and

means to gate said electrical pulses whereby said pulses are countedonly wherever said linear motion is in one direction.

5. In an earth borehole drilling system having a drilling rig whereindrill pipe and associated drill bit penetrate the earths surface, a rateof penetration sub-system comprising:

means to translate the linear motion of the drill pipe into rotarymotion;

means to translate said rotary motion into a series of time-spacedelectrical pulses;

a single shot multivibrator responsive to said electrical pulses;

an operational amplifier responsive to the output pulses from saidmultivibrator, whereby the voltage output from said amplifier isproportional to the frequency of said electrical pulses, said voltageoutput providing an indication of rate of penetration.

6. The sub-system according to claim 5 including, in addition thereto,means for recording said indication of rate of peneration as a functionof the depth of penetration.

7. In an earth borehole drilling system having a drilling rig whereindrill pipe and associated drill bit pentrate the earths surface, acombined rate of penetration and depth of penetration sub-system,comprising:

means to translate the linear motion of the drill pipe into rotarymotion;

means to translate said rotary motion into a series of time-spacedelectrical pulses; amplifier meansresponsive to said time-spacedelectrical pulses, the voltage output of said amplifier providing anindication of the rate of penetration; and

means to count said time-spaced electrical pulses, whereby said countprovides an indication of the depth of penetration.

8. The sub-system according to claim 7 including, in addition thereto,means for recording said indication of the rate of penetration as afunction of the depth of penetration.

9. In an earth borehole drilling system having a drilling rig whereindrill pipe and associated drill bit penetrate the earths surface, atotal depth of penetration sub-system comprising:

means to translate the linear motion of the drill pipe into a series ofelectrical pulses;

means to count said electrical pulses, whereby said count provides anindication of the depth of penetration; and

means to gate said electrical pulses whereby said pulses are countedonly wherever said linear motion is in one direction.

10. In an earth borehole drilling system having a drilling rig whereindrill pipe and associated drill bit penetrate the earths surface, a rateof penetration sub-system coinprising:

means to translate the linear motion of the drill pipe into a series ofelectrical pulses;

a single shot multivibrator responsive to said electrical pulses;

an operational amplifier responsive to the output pulses from saidmultivibrator, whereby the voltage output from said amplifier isproportional to the frequency of said electrical pulses, said voltageoutput providing an indication of rate of penetration.

11. The sub-system according to claim including, in addition thereto,means for recording said indication of rate of penetration as a functionof the depth of penetration.

12. In an earth borehole drilling system having a drilling rig whereindrill pipe and associated drill bit penetrate the earths surface, acombined rate of penetration and depth of penetration sub-system,comprising;

means to translate the linear motion of the drill pipe into a series oftime-spaced electrical pulses;

amplifier means responsive to said time-spaced electrical pulses, thevoltage output of said amplifier providing an indication of the rate ofpenetration; and

means to count said time-spaced electrical pulses, whereby said countprovides an indication of the depth of penetration.

13. The sub-system according to claim 12 including, in addition thereto,means for recording said indication of the rate of penetration as afunction of the depth of penetration.

14. In an earth borehole drilling system having a drilling rig whereindrill pipe and associated drill bit penetrate the earths surface, adrill pipe rate of rotation sub-system, comprising:

a traveling block and kelly assembly, wherein said kelly rotates at thesame rate of rotation as said drill pipe during a drilling operation;

a non-rotating swivel assembly attached to said kelly assembly;

switch means mounted on said swivel assembly;

means mounted on said kelly for activating said switch means as saidkelly rotates; and

electrical circuit means responsive to the closure of said switch meansto provide an indication of the rate of rotation of said drill pipe.

15. The sub-system according to claim 14 wherein said means mounted onsaid kelly comprises a sensor with a permanent magnetic field and saidswitch means is responsive to interruption of the magnetic field by arotating metallic block.

16. ln an earth borehole drilling system having a drilling rig and atleast one mud pit associated therewith, wherein the drill pipe andassociated drill bit in the system penetrate the earths surface,comprising:

means for producing a first linear electrical signal indicative of thetotal mud volume in said at least one mud pit, said means having anoutput following a first given calibration slope;

means for producing a second linear electrical signal indicative of therate of revolution of said drill bit,

said means having an output following a second given calibration slope;

means for producing a third linear electrical signal indicative of therate of penetration of said drill bit, said means having an outputfollowing a third given calibration slope;

first, second and third amplifier means responsive, re-

spectively, to said first, second and third electrical signals, each ofsaid amplifier means having adjustment means for matching the slope ofthe output voltage of the amplifier with the given calibration slope ofits respective electrical signal producing means; and

means for providing a correlative indication of the output voltages ofsaid amplifies.

17. The system according to claim 16 including, in addition thereto,means for converting the output voltages from said amplifiers intodigital signals.

18. The system according to claim 17 including, in addition thereto,means for recording said digital signals.

19. In an earth borehole drilling system having a drilling rig and atleast one mud pit associated therewith, wherein the drill pipe andassociated drill bit in the system penetrate the earths surface,comprising:

means for producing a first electrical signal indicative of the totalmud volume in said at least one mud pit;

means for producing a second electrical signal indicative of the rate ofrevolutions of said drill bit;

means for producing a third electrical signal indicative of the rate ofpenetration of said drill bit; multiplexer means connected to saidfirst, second and third electrical signals;

means connected to said multiplexer means for converting said electricalsignals into-digital signals; and means for providing a correlativeindication of said digital signals.

References Cited UNITED STATES PATENTS 2,287,819 6/1942 Nichols 73-151.5X 2,539,758 1/1951 Silveman et al. 73--151.5 2,807,678 9/1957 Rapp330-96 X 3,445,767 5/1969 Beard.

JERRY W. MYRACLE, Primary Examiner U.S. C1. XR. 73-149, 151.5

